Gear-cutting machine.



W. ANDERSON -& T, COVENTRY.

GEAR CUTTING MACHINE. APPLICATION F |LED MAR. 7. 19'14.

Patented Feb. 29,1916.

W 7% 5a N m R #mMW N0 E M. ma R IMA- WITNESSES ,4 Min u THE COLUMBIAPLANOGRAPH .60., WASHINGTON, n. c.

sra rns Parana ent ies.

WILLIAM ANDERSON, OF ALTRINCI- IAM, AND THEODORE COVENTRY, 0F SALFORD,ENGLAND.

GEAR-CUTTING MACHINE.

Specification of Letters Patent.

Application filed March 7, 1914. Serial No. 823,254.

To all whom it may concern Be it known that we, WILLIAM ANDERSON, of 122Hale road, Altrincham, in the county of Chester, England, and THEODORECOVEN- TRY, of Gresley Iron Works, Salford, in the county of Lancaster,England, subjects of the King of Great Britain and Ireland, haveinvented certain new and useful Improvements in Gear-Cutting Machines,of which the following is a specification.

This invention relates to bevel wheel and like gear cutting machines ofthe type in which cutting tools, operating simultaneously on both sidesof a tooth, are reciprocated on automatically adjusting or opening andclosing guide arms in lines or paths always directed toward the apex ofthe pitch cone of the wheel. Such a machine is described in U. S. PatentNo. 668772.

The object of our invention is to provide improved means for giving therequired automatic opening and closing movements to the guide armsduring the cutting operation so as to produce the correct involute orother tooth form.

Our invention comprises the combination with the guide arms on which thecutting tools are reciprocated, of a dummy or former, having twosurfaces of correct configuration, adapted to act upon said guide armsand to be traversed through an adjustable distance for the purposehereinafter described.

Referring to the accompanying sheet of explanatory drawings :Figure 1 isa front elevation and Fig. 2 an end elevation of part of a gear cuttingmachine having our invention applied thereto.

The same reference letters in the two views indicate the same parts.

In the application of our invention, we arrange the guide arms a inwhich the tool slides are traversed in the usual manner and pivot sameabout a point which is the apex of the pitch cone of the bevel wheelsbeing out. Each of said arms has a slot 6 therein at its free end and ascale thereon, a bracket 0 being adapted to be fixed in the slot at acertain position indicated on the scale according to the pitch of thewheel being cut. Each bracket carries a roller d which bears upon asurface of involute configuration of a dummy or former 6. Thus oneroller bears upon the upper and one upon the lower side of the former.The latter is mounted upon a slide 7 which is traversed or reciprocatedby means of the quadrant 9 connecting rod h and arm 2' whichsynchronize'in their movements with the feed movements given to theblank during the cutting operations. The arm 6 is actuated by means suchas employed in the prior U. S. patent before referred to for actuatingthe similar arm d". The rate of movement and length of traverse of theslide f may be adjusted by varying the position of the end of the rod hin the arm 2' so that the rollers (,5 may traverse a greater or lessportion of the'former surface during the cutting of a complete tooth andthus the an gular distance through which the guide arms a are moved beincreased or diminished to suit the pitch of tooth and its correspondingcurvature.

In operation, when for example a miter wheel of a certain tooth pitch isbeing cut, the blank axis is set at an angle of 45 degrees to the pathof the cutting tools. The brackets 0 in the guide arms a are adjusted inposition to suit the tooth pitch, and the rollers all each contact withthe former at a point on the pitch line of the dummy. The parts beingnow locked in position, all movements of the blank saddle arecommunicated to the former.

To provide for the correct formation of teeth in bevels of varyingangles, the distance through which the former e is traversed during eachstroke of the cutting tools is adjusted so that a more or less extendedportion of the former is traversed by the rollers contacting therewith.This arrangement provides for a variation in the total angular movementimparted to the guide arms a and therefore a variation in the startingand finishing positions of the cutting tool, in the involute path.

We preferably provide a counter-weight j which tends to press the lowerbracket 0 upward. The effective weight of the said counterweight ispreferably twice the weight of said bracket 0 and the roller cl thereon.Thus when the two brackets are freed from the guide arms a for settingpurposes, the pressure of the upper bracket upon the former will beexactly the same as the pressure of the lower bracket thereon.

The guide arms a, are balanced against one another by means of a steelband represented by is and when the machine is in operation the twobrackets balance one another,

the pressure upon the two surfaces of the former 6 being that of thecounterweight j onl INith our improved arrangement, bevel gears of anyangle or ratio can be accurately cut, and likewise by varying the shapeof the former, teeth having different pressure angles of any ratio canbe 7 generated. Further as the former is traversed by copying rollerscl, the cutting operation may be accurately performed by round nosedtools having a radius proportional to theradius of the copying rollersand to the distance of the tool from the apex of the pitch cone whencutting.

Having now described our invention, what we claim as new, and desire tosecure by Letters Patent is w l.' In a gear cutting machine havingreciprocating cutting tools operating simultaneously on both sides of atooth, the combination with the guide arms carrying the said cuttingtools, of a dummy or former having two opposite sides of correctconfiguration, means for traversing the said dummy or former throughadjustable distances during the reciprocation of the cutting tools andmeans whereby the movements of the dummy or former impart the requiredopening and closing movements to In testimony whereof we have signed ournames to this specification in the presence of two subscribingwitnesses. V

IVILLIAM ANDERSON.

THEODORE COVENTRY.

Witnesses: v

ARTHUR HUGHES, MALCOLM SMETHURST.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, I C.

